A telecommunications system may include a distributed antenna system (“DAS”) or a repeater that may be used to extend the coverage of a cellular communication system. For example, a DAS may extend coverage to areas of traditionally low signal coverage within buildings, tunnels, or in areas obstructed by terrain features. A DAS may include one or more head-end units in communication with carrier systems, such as base transceiver stations of cellular service providers. The DAS may also include remote units physically separated from the head-end unit, but in communication with the head-end unit via a serial link that may be copper, optical, or other suitable communication medium.
The remote units may wirelessly communicate with user devices positioned in a coverage area. For example, the remote units may be positioned in a building, tunnel, or other structure that prevents or limits communications directly with the carriers. Remote units amplify downlink signals received from the base station via a head-end unit and radiate the downlink signal using an antenna. The remote unit recovers uplink signals from mobile user equipment and provides the uplink signals to the head-end unit. The uplink signals may be summed together and provided back to the base station.
A remote unit may include at least one duplexer. The duplexer may isolate a transmitter output from a receiver input by allowing frequencies within the downlink band to be provided from the transmitter output to the antenna and allowing frequencies within the uplink band to be provided from the antenna output, input, respectively, to the receiver.